Encephalitis

Encephalitis is an acute inflammatory disease of the brain. Its origins may be bacterial, viral, or in some cases, unknown. In certain locations, it is not uncommon for the viral source to be mosquito or tick-borne. Other means of viral transmission include ingestion of infected goat's milk and accidental injection or inhalation of the virus.

In urban areas where mosquitoes are less prevalent, the disease is more commonly caused by a group of viruses called enteroviruses, that is, viruses that multiply primarily in the intestinal tract. An increasing number of cases are caused by infection with the human immunodeficiency virus (HIV). Encephalitis can also occur as a secondary complication following viral infections such as measles, chickenpox, rubella, and mumps. Sporadic encephalitis is most commonly due to the herpes simplex virus.

Encephalitis can be a serious life-threatening medical condition, but can also be so mild that it is barely noticeable. Specific prevalence and incidence statistics are unknown, but the condition seems to occur more frequently in individuals with multiple sclerosis who are not functioning at optimum levels (immunosuppressed), and in areas where virus-carrying insects are prevalent. Encephalitis is found throughout the western hemisphere, predominantly in the eastern regions of North, Central, and South America and throughout the US.

Incidence and Prevalence It is impossible to determine true incidence, since reporting policies are not standardized or rigorously enforced and incidence varies with the etiology of the encephalitis. A majority of encephalitis is from infection with viruses and it affects 3.5 to 7.4 out of 100,000 individuals annually; the most frequent cause of sporadic encephalitis is herpes simplex encephalitis (HSE), affecting 2 Americans per million annually {de Assis Aquino Gondim}.

History The initial symptoms are a vague feeling of discomfort or illness (malaise), fever, headache, loss of appetite (anorexia), and nausea. Symptoms progress to confusion and subtle changes in personality. In later stages, mental disturbances become more apparent and there may be difficulty talking (dysphasia), weakness, seizures, severe disorientation, and coma. In secondary viral encephalitis, the disease may develop 5 to 10 days after onset of an initial viral infection such as mumps, measles, or chickenpox. The individual may be from, or have recently traveled to, a region where mosquitoes and/or ticks are prevalent and been bitten. Individuals may report a recent viral infection, such as measles, mumps, or chickenpox. They may also complain of a back or neck ache.

Physical exam There is evidence of fever, a stiff neck and/or back, tremors, seizures, paralysis of extremities, abnormal walk (gait), and abnormal reflex reactions. Deep loss of consciousness (coma) may occur and last for days or weeks. Encephalitis might be suspected when there is a change in mood along with headache and fever. A change in alertness or consciousness may also point the physician toward the diagnosis.

Tests A lumbar puncture may reveal increased pressure of the cerebrospinal fluid and is used to collect spinal fluid for analysis, which may show increased protein content and cell count (usually lymphocytes). A CT or MRI of the brain may detect lesions in the lobes of the brain near the temple and ear (temporal lobe lesions) caused by a herpes viral infection. Measuring the electrical activity of the brain by electroencephalography (EEG) is also useful to diagnose herpesvirus encephalitis, but a sample of brain tissue collected for microscopic examination (brain biopsy) is usually necessary to confirm this diagnosis and exclude other treatable diseases. Occasionally, taking a sample of the individual's blood during the disease and comparing it with a sample after the disease has resolved (acute and convalescent antibody titers) may be the only way of making a specific diagnosis of a viral infection. Polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA) can be used to identify certain viruses.

Treatment of all forms of encephalitis, other than herpes encephalitis, is entirely supportive. Supportive measures are used to maintain the individual's hydration, electrolyte balance, and nutritional needs. Supportive treatment includes fluids, nutrients, and electrolytes given intravenously. In otherwise stable individuals, elevating the head and monitoring the neurologic status are supportive measures. Medication may be needed to reduce fever (antipyretics), intracranial pressure, and inflammation (glucocorticoids), and to prevent seizures (anticonvulsants). Pain medication (analgesic) is given to reduce headache.

When more aggressive treatment is indicated, the use of diuresis may be recommended, provided that circulatory volume can be protected.

Herpes simplex encephalitis is also treated with an antiviral medication (acyclovir) specific to treating herpes simplex viral infections.

The origin of the encephalitis determines prognosis. For HSE the death rate was 70% without medical intervention {de Assis Aquino Gondim}. In mild cases, full recovery occurs within 2 to 3 weeks. Eastern equine encephalitis is associated with severe disease and high mortality rates. Severe cases usually require hospitalization and leave significant mental impairment including memory loss, the inability to speak coherently, lack of muscle coordination, paralysis, and hearing or vision defects. Individuals under the age of 30 and those only lethargic at the onset of treatment are more likely to survive than individuals who are older or comatose.

Individuals with encephalitis may require physical, occupational, and speech therapy depending on the impairments present. Individuals with encephalitis may present with lack of muscle coordination, decreased balance, paralysis, hearing and vision deficits, and an inability to speak coherently. The frequency and duration of rehabilitation should be determined by the severity of impairments.

Individuals with encephalitis may have impaired coordination. In occupational therapy, individuals perform fine motor coordination exercises. In physical therapy, individuals work on gross motor coordination. Individuals work on sitting and standing balance in both physical and occupational therapy. Sitting balance can be improved by having an individual sit on a therapy ball. Physical therapists may focus on exercises to improve standing balance in order to preserve the ability to walk.

Individuals who present with paralysis also require physical and occupational therapy. Both disciplines instruct caregivers about stretching programs for the arms and legs in order to maintain adequate flexibility. Occupational therapists instruct individuals in self-care strategies, and may order adaptive equipment to make tasks easier. Occupational therapists also instruct individuals in methods to make self-care easier. Physical therapists instruct individuals in gross motor skills. Physical therapy also addresses walking, and individuals learn to walk using crutches or leg braces, where appropriate. For those individuals who cannot safely ambulate, a wheelchair may be ordered. Individuals learn to propel the wheelchair both indoors and outdoors, over ramps and curbs.

Individuals with decreased vision may require occupational or physical therapists to make a home safety assessment. Therapists can identify tripping hazards, and can assist in rearranging the layout of rooms to increase safety. Physical therapists can instruct individuals on how to use a cane to help them negotiate stairs. Occupational therapists can order equipment that may make daily living easier, such as a telephone with larger numbers.

Individuals who present with the inability to speak coherently may require speech therapy. Speech therapists focus on skills such as word finding and sentence completion. Individuals and their caregivers may also learn methods to increase concentration, such as providing a low-stimulus environment in order to decrease distractibility.

Individuals with difficulty hearing may require speech therapy to learn new strategies for communication. Individuals may learn to read lips or utilize sign language. Individuals may also learn how to use amplification devices and hearing aids to increase their hearing.

Restrictions or accommodations need to be considered on an individual basis since the severity and complications of encephalitis are variable. If there are lingering speech and motor/coordination problems, job duties may need to be reassessed depending on the nature of the job. Responsibilities requiring significant amounts of public speaking may be in jeopardy if there is permanent speech impairment. Jobs requiring a great deal of mobility and physical labor may also need to be reassessed.

Possible complications include seizures, brain damage that causes loss of sensation, coordination, and power in specific areas of the body, and/or speech difficulties, and death. The membranes that cover and enclose the brain (meninges) may also be involved, and these membranes may become inflamed (meningoencephalitis).

The severity of the inflammation and symptoms, involvement of other nervous system structures, the individual's response to treatment, the presence of complications, and any permanent brain damage may influence length of disability.

Length of disability will depend on job requirements, response to treatment, and presence and severity of any cognitive impairment. Disability may be permanent if mobility, coordination, and strength are affected and the individual's job requires significant manual labor. Contact physician for additional information.

If an individual fails to recover within the expected maximum duration period, the reader may wish to consider the following questions to better understand the specifics of an individual's medical case.

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